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We're about to do a major office move, which will involve re-cabling everything in our premises. We're in two floors of a single office building, with 2-4 comms cabinets on each floor; each of these cabinets contains a Catalyst 3560; currently these are all connected to a single "core" switch (also a 3560) that joins everything together. Each floor currently has its own structured cabling setup, with all cabling run back to the patch panel in the cabinet for that floor.

During the move/re-cable, we're going to do away with this setup, cable everything into a single comms rack and move all the switches into there, so I'm wondering about the best way to connect five or six Catalyst 3560s together.

I notice that Cisco sell an SPF interconnect cable for the 3560, but should I go for these? If I'm reading the spec properly, they provide a gigabit connection between two or more Catalysts; why is this better than just connecting two of the standard gigabit ports, or etherchanneling several of them together to provide a multi-gigabit "backbone"?

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I believe you're right and that a single or etherchannel'ed link will provide everything you'll need over regular ports. It's a pity that box doesn't have a stackwise port though :(

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OK, so let's ignore the SPF cable. Could I connect switches 1 and 2 to each other with a 4-port etherchannel (4Gb/s), and then each of the other switches to both switch 1 and switch 2 with separate 2-port etherchannels (2Gb/s), as radius suggests? Does that sound reasonable? –  RainyRat Jul 16 '10 at 10:49
    
Yes, you can do that. –  Chopper3 Jul 16 '10 at 11:03
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I've been disappointed in Cisco's "stacking" story in their lower-end switches for the last few years. A dedicated, multi-gigabit stacking interface would be a welcome addition, but then they wouldn't be "lower-end" anymore, I suppose... –  Evan Anderson Jul 16 '10 at 11:43
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I'm lucky Evan, I get to use Nexus and Cat65's but for some of our smaller labs we've used some 3750s and the stacking capabilities are 'ok' - I wouldn't like to rely on them though. –  Chopper3 Jul 16 '10 at 11:54

So you have 6 3560 + the core one, right ? You can't use the SPF interconnect cable because at max (depending of the model) you have ony 4 SPF port on the core switch. So you can't connect 6 switch using this.
This would involve connecting SW1 to SW2, SW2 to SW3, SW3 to SW4, etc.. this is not a good network design.
You don't give model details but the best option would be to have 2 3560 with 10/100/1000 ports, let's say it's SW1 and SW2. Connect SW1 to SW2 then connect each others SW to both SW1 and SW2 so that you have a perfect redundancy if SW1 or SW2 stop to work.

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